The invention relates to an omnibus track guidable vehicle for special roads having at least one vehicle non-steerable by itself axle which has an axle body pivotable about an upright vertical axis central of the vehicle width and staggered in the longitudinal direction of the vehicle relative to a center line of the vehicle. A pair of pull rods are provided which extend generally in a longitudinal direction of the vehicle, one on each side of the vehicle center axis. The pull rods are articulated to the axle body. Guide rods are provided, articulated to the axle body for retaining the vehicle axle in a transverse direction. The guide rods and the pull rods act in concert to prevent a rotation of the vehicle axle in, or counter to, the direction of rotation of the vehicle wheels. A yawing vibration brake is provided for attenuating yawing vibrations of the vehicle axle.
Track guidable omnibusses with transverse guidance by transverse guidance bars fitted on both sides of the special road and cooperating with transverse guidance rollers on the vehicle have problems when it comes to making the trailing axles follow the foreward track guided vehicle axle in the correct track on curves. According to DE-OS No. 2,643,324, the trailing vehicle axle is mounted in a pivotably bogie fashion. A track determining transverse guidance roller for each vehicle side is provided preceding and following the trailing axle. A total of four transverse guidance rollers, which are permanently in contact with the transverse guidance bars on the road are therefore provided for each trailing axle. The direction of the track determining transverse guidance bars is imprinted positively upon the pivotable trailing axle by these guidance rollers. The pivot center of the vehicle axle, which is non-steerable by itself but is pivotable, is dictated mechanically by fifth wheel segments and by the intersection of a pair of three-bar linkages. In view of the pivotable trailing vehicle axle running free from yawing vibrations, this pivot center lies in front of the axle center in the direction of travel. To enable braking and traction moments to be absorbed reliably during the pivoting of the trailing vehicle axle, pull rods are made variable in length by integrated piston/cylinder units. The chambers of these piston/cylinder units, arranged on the right and on the left side of the vehicle being mutually interconnected. Consequently, a pivoting of the trailing axle is possible, but not a rotation of the axle body either in, or counter to, the direction of rotation of the wheels. These piston/cylinder units may also serve as a yawing vibration brake in common with a connection with a throttling action. In view of the fact that the wheels of the pivotable trailing vehicle axle are always aligned precisely parallel to the track determining transverse guidance bars, the wheel plane of the vehicle wheels always coincides with the direction of travel. It is impossible for an oblique angle to develop between wheel plane and direction of travel. Consequently, transverse forces which occur, have to be absorbed completely by the track determining transverse guidance rollers and are transmitted into the transverse guidance bars. The transverse guidance rollers are therefore stressed permanently and very highly when transvers forces occur and thus they must be dimensioned correspondingly to accept this loading. This raises problems of space and weight. The pivotable guidance of the trailing vehicle axle by means of fifth wheel segments or by means of a complete fifth wheel is also highly onerous and heavy. Nonetheless, in view of the fastening of the axle, a maximum of seven degrees of angle pivoting stroke can be permitted at each side. Although the majority of curves which occur can be travelled with correct tracking with such a pivot angle, tighter curves also occur which would necessitate an even greater pivot angle of the trailing vehicle axle. To enable even such curves to be negotiated without obstruction, the transverse guidance bar on the road on the inside of the curve must be offset inwards, so that the trailing vehicle axle can trail offset towards the inside of the curve. A disadvantage of this mode of vehicle axle trailing, in correct tracking within the track determining special road, lies in the expensive, complicated and heavy construction of the trailing vehicle axle and its suspension, which involves various operational disadvantages. Also, in the transition to trackless manually steered operation, the pivotable vehicle axle must be provided with an onerous transverse position locking means which cancels out the pivotability. This increases the expense and complicates the axle construction to a further degree.
This costs in money, space and cumbersome mechanisms has not in fact been undertaken in the practical construction of omnibusses, but essentially a rigid and immovably mounted trailing vehicle axle has been retained. A so-called push roller has been associated on each side of the trailing vehicle axle, which rollers project only slightly beyond the side flanks of the vehicle wheels so that they do not come into contact with the track determining transverse guidance bars normally, but only in curves. When travelling curves these push rollers push the vehicle forcibly towards the outside of the curve, so that the trailing vehicle axle can follow the track determining road even without pivoting. When travelling a curve slowly, when virtually no centrifugal forces occur, the trailing vehicle axle has a tendency to trail offset towards the inside of the curves. When travelling a curve slowly, the push roller on the inside of the curve is therefore stressed, and in fact more strongly stressed as the curve is made tighter. With increasing speed of travel in curves, an influence of centrifugal force occurs, which tends to push the vehicle to the outside of the curve. This causes a relief of the push roller on the inside of the curve at moderate speeds of travel. At a suitable speed when travelling a curve, a condition may arise in which the trailing vehicle axle rolls between the track determining transverse guidance bars with correct tracking even without contact of the push roller. In this travel condition, the outwardly directed influence of centrifugal force and the inwardly directed tendency to lateral offset the trailing vehicle axle just cancel each other. When travelling a curve even faster, the influence of centrifugal force may predominate, so that in such a condition the push roller on the outside of the curve contacts the associated transverse guidance bar and is more or less heavily stressed depending upon the valve of the speed of travel and corresponding centrifugal force. This travelling condition can arise in practice when the existing track determining roads are travelled at relatively high travelling speeds. In vehicles which have no push rollers on the trailing vehicle axles, the outer flank of the vehicle wheels comes into contact with the track determining transverse guidance bar, so that the tire is chafed on the side flank in a relatively short time. Although it is possible to travel through a track determining road without contact, even without push rollers on the trailing vehicle axles, it is necessary for this purpose to adhere to a quite specific speed range, which is a function of the radius of curvature of the curve and of the degree of the banking of the road in the region of the curve. These two together determine the so-called design speed of a curve. Experience has shown that the range of speeds with which a curve can be travelled with correct tracking by the trailing vehicle axle without contact, is narrower as the design speed of the curve is higher. In such cases, even slight excesses of the design speed result in an outside chafing of the tires or in an outside contact of the push roller. When travelling too slowly the tires on the inside of the curve chafes at the side, or the push roller on the inside of the curve contacts the transverse guidance bar. Although the chafing of the tire flanks against the transverse guidance bar can be prevented by the installation of push rollers, nonetheless the latter are also not problem free, because frequently they cannot be accommodated for reasons of space, and because if they are small, they can be stressed only lightly or only for a short time. Under protracted high stress, the push rollers become worn relatively quickly, particularly if they are used in hot climates and can become heated inadmissibly intensely by thermal absorption from the transverse guidance bars, intensely by solar radiation and intensely due to self-heating by rolling friction in the covering of the push roller.
The object of the invention is to develop a track guidable vehicle omnibus which is of simple construction in the region of the trailing vehicle axle and which, even without push rollers, can travel through the special road without contact by the trailing vehicle axle within a relatively wide range of speeds around the design speed of a curve.
In order to achieve this object the invention, the non-steerable by itself vehicle axle is free as concerns pivoting without engagement by the track guidance rails and pivots as a function of transverse acting forces in a pivotal range of approximately .+-.0.8 to 1.5 degrees of angle around an exact transverse position and elastokinematically counter to the direction of the transverse force. This pivoting is due to the articulation of the guide rods which restrain the axle body of the vehicle non-steerable by itself axle in the transverse direction. Further, the axle body is transversely and limitedly slidable transversely of the vehicle longitudinal control axis as a function of the transverse force applied. This limited sliding is equal t a distance approximately .+-.0.8 to 1.2 % of the vehicle width with the actual amount of sliding being proportional to the amount of force being applied. The pull rod means are provided to be unyielding in the longitudinal direction and are inclined symmetrically with respect to the vehicle central axis, as viewed in plan in the longitudinal direction of the vehicle, to define a trapezoid. An intersection of a kinematically effective center lines of the plural pull rods constitutes the vertical pivot center for the axis body means and is located approximately in the direction of travel of the vehicle behind the vehicle non-steerable by itself axle at a distance approximately equal to 50 to 100% of the vehicle width.
This provides an omnibus vehicle having a trailing vehicle axle connected conventionally to the vehicle body, in which the elements of the axle suspension, which are always present in any case, are modified in themselves and/or installed in a modified way. Where an additional structural outlay is necessary, it is only slight and requires scarcely any additional space or weight. The improved tracking ability of the trailing vehicle axle across a wider range of speeds around the design speed of a curve is possible because of a greater oblique running angle between the wheel plane and direction of travel and can be adjusted automatically as a function of the transverse forces applied. This pivot angle, which results from the pivotability of the trailing vehicle axle, is added to the oblique running angle which is adjusted automatically. Even with the rigid rear axle, when the vehicle is travelling at design speed with correct tracking and without contact with the track through a curve of a track determining road, an oblique running angle exists between wheel plane and direction of travel, due to which the vehicle wheels can absorb transverse force due to centrifugal force and transmit it into the road. By virtue of the pivotability according to the invention, this oblique running angle is increased by the angular amount of the pivotability of the trailing vehicle axle, so that the trailing vehicle axle has an increased load capacity in the transverse direction. In particular, the range of speeds at which a curve can be travelled without contact and with correct tracking has been considerably widened. Therefore a side contact of the push rollers, which are recommended for security, can be restricted to a few extreme cases in which a temporary stressing of the push rollers is acceptable.
An additional advantage is obtained by having the guide rods, which provide for the transverse sliding of the vehicle axles, to be telescoping in nature and thus to effect the limited movement by limiting the amount of telescoping of these guide rods. An expedient manner of providing for this telescoping is by the use of a piston in a cylinder, which piston is constructed with a circular rubber/metal sleeve means which limits and centers the piston in the cylinder. The ends of the cylinder can also be provided with a similar circular rubber/metal sleeve which grasps the rod of the piston. This piston can also serve as the hydraulic yawing vibration brake for the vehicle.
Another feature of the invention is to have guide rods which restrain the vehicle axle in the transverse direction to act in concert with the push rods to also secure against rotation in, or counter to, the direction of rotation of the wheels by means of forming these guide rods as a pair of three bar linkages placed triangularly as viewed in plan. Each pair of these three bar linkage means are connected articularly at an end to a rocker arm connected to the vehicle axle body to form a trapezoidal four bar linkage. The connection of the rocker arm to the axle body is obtained by an articulation joint arranged centrally of the rocker arm. With this type of operation, a buffer means can be provided to abut the guide rod to restrain the transverse movement The articulation joint can also be constructed as a rubber/metal bearing to provide a centering effect on the rocker arm itself. The rocker arm can also have an extension member extending beyond the guide rod and which has a hydraulic shock absorber attached thereto which will serve as a yaw vibration brake.
Additionally, a pair of push roller means can be mounted on the axle body means ahead of the vehicle wheels on both sides of the vehicle to provide for restricted contact with the track when, in those rare instances, excess forces are applied. In order to keep these push roller means from contacting the rails normally, they are located one apart from the other a distance greater than the width of the outside of the vehicle wheels on the axle, but less than the distance between the vehicle rails which define the guidance path for the track guidable vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings